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Rollup merge of #92011 - Aaron1011:decode-span, r=michaelwoerister

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Use field span in `rustc_macros` when emitting decode call

This will cause backtraces to point to the location of
the field in the struct/enum, rather than the derive macro.

This makes it clear which field was being decoded when the
backtrace was captured (which is especially useful if
there are multiple fields with the same type).
This commit is contained in:
Matthias Krüger 2022-01-03 14:44:16 +01:00 committed by GitHub
commit fd09f342f3
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1 changed files with 15 additions and 11 deletions
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26
compiler/rustc_macros/src/serialize.rs
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@ -1,6 +1,7 @@
use proc_macro2::TokenStream;
use quote::quote;
use quote::{quote, quote_spanned};
use syn::parse_quote;
use syn::spanned::Spanned;
pub fn type_decodable_derive(mut s: synstructure::Structure<'_>) -> proc_macro2::TokenStream {
let decoder_ty = quote! { __D };
@ -104,6 +105,8 @@ fn decode(
}
fn decode_field(field: &syn::Field, index: usize, is_struct: bool) -> proc_macro2::TokenStream {
let field_span = field.ident.as_ref().map_or(field.ty.span(), |ident| ident.span());
let decode_inner_method = if let syn::Type::Reference(_) = field.ty {
quote! { ::rustc_middle::ty::codec::RefDecodable::decode }
} else {
@ -111,20 +114,21 @@ fn decode_field(field: &syn::Field, index: usize, is_struct: bool) -> proc_macro
};
let (decode_method, opt_field_name) = if is_struct {
let field_name = field.ident.as_ref().map_or_else(|| index.to_string(), |i| i.to_string());
(
proc_macro2::Ident::new("read_struct_field", proc_macro2::Span::call_site()),
quote! { #field_name, },
)
(proc_macro2::Ident::new("read_struct_field", field_span), quote! { #field_name, })
} else {
(
proc_macro2::Ident::new("read_enum_variant_arg", proc_macro2::Span::call_site()),
quote! {},
)
(proc_macro2::Ident::new("read_enum_variant_arg", field_span), quote! {})
};
let __decoder = quote! { __decoder };
// Use the span of the field for the method call, so
// that backtraces will point to the field.
let decode_call = quote_spanned! {field_span=>
::rustc_serialize::Decoder::#decode_method(
#__decoder, #opt_field_name #decode_inner_method)
};
quote! {
match ::rustc_serialize::Decoder::#decode_method(
__decoder, #opt_field_name #decode_inner_method) {
match #decode_call {
::std::result::Result::Ok(__res) => __res,
::std::result::Result::Err(__err) => return ::std::result::Result::Err(__err),
}